It is well known that automobile engines tend to form deposits on the surface of engine components due to oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or deposit control additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
Polybutene fuel additives, such as polybutene amines and polybutene succinimides, are examples of fuel additives well known in the art. They aid in decreasing deposits in intake valves and port fuel injectors of internal combustion engines. However, they have been considered to contribute to, rather than reduce combustion chamber deposits. Because it was widely believed that increasing concentrations of such fuel additives would lead to an increase in combustion chamber deposits, commercial polybutene fuel additive concentrations were typically below 300 ppm. The prior art does not teach that the polybutene amine can actually give better combustion chamber deposit control than the base fuel alone.
U.S. Pat. No. 3,438,757 teaches using a hydrocarbyl-substituted amine with mineral oil. The amine is added at from 100 to 1,000 ppm.
U.S. Pat. No. 3,785,789 teaches using the reaction product of a hydrocarbyl-substituted amine and a coupling agent with mineral oil. From 100 to 4,000 ppm of the reaction product may be present in the fuel. Preferably, from 200 to 800 ppm is used. The only concentration used in the examples is 1,000 ppm.
U.S. Pat. No. 4,877,416 teaches using a hydrocarbyl-substituted amine or polyamine and a poly(oxyalkylene) monool. The amine is added at from 10 to 10,000 ppm (preferably 200 to 1,000 ppm). No example was given of an actual fuel composition, and there was no teaching that the polybutene amine actually gives better combustion chamber deposit control than the base fuel alone.